The present invention relates to a luminance signal noise suppressor for a television receiver, a video tape recorder, a television tuner and the like, and relates to suppressors able to automatically suppress noise in video signals input with much noise in weak electric field receiving regions or zones.
In recent years, as color television receivers have become larger a problem has arisen of noise included in a video signal such that the noise is also more conspicuously viewable on their large size displays. Thus a luminance signal noise suppressor which suppresses noise in a video luminance signal for the purpose of displaying a picture image more clearly has been regarded as important particularly in a weak electric field zone. On the other hand, there are many strong electric field zones depending on the broadcasting channel, and it is required for conventional receivers to put turn such a noise suppressor ON/OFF every time the receiving channel is selected, which gives rise to a problem of complexity in operation.
An example of such conventional luminance signal noise suppressors will be described hereafter with reference to the drawings.
FIG. 4 shows a block diagram of a conventional luminance signal noise suppressor. In FIG. 4, a noise suppression circuit 21 reduces noise of an input luminance signal a and outputs an output luminance signal f. A switch 22 is operated to enable or disable the noise suppression circuit 21. The operation of a luminance signal noise suppressor constructed as described above will now be described.
First, the input luminance signal a is input to the noise suppression circuit 21, which suppresses or eliminates noise in accordance with a state of the switch 22, or the inputted signal is otherwise output as the output luminance signal f.
In the above-described construction, however, it is required to turn the switch 22 ON for a signal including much noise in case of a weak electric field signal, and to turn the switch 22 OFF every time for a signal including comparatively less noise in case of a strong electric field signal since detail information of a video signal are generally missing in a state that the noise suppression circuit 21 is ON. These operations are disadvantageously complicated.